RE: Cermark Pitts Build/Assembly

RE: Cermark Pitts Build/Assembly
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RE: Cermark Pitts Build/Assembly - 3/13/2007 2:05:15 AM

V2PLUS10

Posts: 662
Joined: 5/31/2003
From: Boise, ID,
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I really don't remember how much time went into assembling the Cermark Pitts. It went together well, but the modifications that I seem compelled to make took a little time....I also had to wait for some items that I could only order after the model had arrived. It didn't take very long though.

I think that as responsive as this model is to aileron input two servos and couplers would be fine. The Saito 180 is kind of heavy, and it is more than enough power. A 120 4-stroke or maybe even a 1.08 two stroke would be enough power. A lighter model would surely fly better as the Pitts is just like it's full scale counterpart in terms of it's high wing loading.

It is a real kick to fly though, and an aerobatic biplane with that Saito 4-stroke sound is tough to beat.

If you get another you will not regret it. Lots of fun and a Pitts always draws a crowd....

Randy

(in reply to airborneSGT)

Post #: 26

RE: Cermark Pitts Build/Assembly - 6/23/2007 1:35:31 PM

apkent

Posts: 5
Joined: 3/11/2006
From: , UNITED KINGDOM
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Hi guys, I'm new here!

Looking to buy one of these lovely looking Pitts but can't decide on a suitable engine. I've ranged from a Moki 1.35 to a Saito 125 and OS120AX. I get the feeling it might be a bit overpowered with the OS 2 stroke, but I'm told will be a little underpowered with the Saito.....

What are your thoughts? I can't really afford the step up to a Saito 150 so the OS and Saito are the only ones in consideration really.....

Cheers,
Andrew

(in reply to V2PLUS10)

Post #: 27

RE: Cermark Pitts Build/Assembly - 6/23/2007 2:28:43 PM

V2PLUS10

Posts: 662
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From: Boise, ID,
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Hi Andrew,

That OS120AX is a great engine. A fellow at the local field has one and it really pulls...I have a Saito 180 in my Cermark Pitts and it has plenty of power, but the heavier engine/muffler assembly, along with the onboard glow driver and battery pack really add to the all-up weight. I also used some Engine vibration eliminators from Apache Aviation which add a little weight but work great.The model is pretty fast....I have not weighed it. I do think the 125 4-stroke would be too little power for aerobatics, probably fine for just crusing around and sport type flying...The OS120AX gets my vote...

Randy

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Post #: 28

RE: Cermark Pitts Build/Assembly - 6/24/2007 3:08:50 AM

doctorgo

Posts: 177
Joined: 7/24/2002
From: ypsilanti, MI, USA
Status: offline

Greetings, Randy.
I have always had wing incidence issues with biplanes. The GP 1/3 Pitts lower wing was way out of line and it was (I sold it) easily the worst flying plane of the 60 I built so far.

My GP Super Stearmans, on the other hand, are absolutely great! But again, the wing incidence was set wrong by design. I corrected it and the three I've done for myself and others, fly perfectly. The wing loading is 21.6 oz / sq ft, based upon its weight of 13 pounds, 12 ounces. With a Thunder Tiger 1.20 turning an APC 16 x 8 at 9200 rpm on 5% Wildcat fuel, it flies much too fast for scale. Obviously, a little less throttle remedies that situation.

In regard to the Cermark Pitts. I know the red model is an old Dave Patrick design. It was not well built at first and Dave's association with Cermark became strained years ago. The blue model looks a bit different than the red.

My question is: are the wing incidence specifications stated in the assembly manual? Does anyone know what they should be? The published specs indicate the model weighs 9-10 pounds. At 10 pounds the wing loading is 22.6 oz / sq ft. Do you consider 22.6 oz to be high?

(in reply to V2PLUS10)

Post #: 29

RE: Cermark Pitts Build/Assembly - 6/24/2007 6:20:58 PM

V2PLUS10

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From: Boise, ID,
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I just weighed the model and I think I'm closer to 12 pounds, probably 12+ using the bathroom scale method..I really do need to buy an accurate scale.... The Saito 180 is almost 10oz heavier than the OS120, and I have an onboard glow driver with a 1400ma battery pack and seperate switch harness. Probably an extra pound total. I also added some wood to the firewall and forward fuselage structure as shown in the build pics. Add to that the two extra aileron servos (four total) and the weight adds up. We are at 2800' msl here also which adds to the inflight speed....it is a really nice flying model though, and if you could keep it within the 9-10 pound range an OS 120 two stroke should be ample power...I already had the Saito so was trying to find a suitable Pitts, which at the time meant either a Great Planes or a Cermark.

I'll see if I can find any reference to wing incidence in the instructions....

Randy

(in reply to doctorgo)

Post #: 30

RE: Cermark Pitts Build/Assembly - 6/24/2007 11:15:42 PM

apkent

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From: , UNITED KINGDOM
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Thanks very much for your replys guys. OS 120 it is then..........

Just shows, always worth a quick post to confirm things in your mind

Thanks again,
Andrew

(in reply to V2PLUS10)

Post #: 31

RE: Cermark Pitts Build/Assembly - 6/24/2007 11:21:41 PM

ram3500-RCU

Posts: 1815
Joined: 8/17/2002
From: n. canton, OH, USA
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I flew mine for several years before selling it.

The Satio 180 proved to be a good fit for the plane as it gave me the power I needed for knife edge loops and such. I used (2) high torque servos for the ailerons instead of going with (4) weaker or standard servos. I also didn't use the on-board glow option, as the Satio idles great and is totally reliable even without it.

I never changed the incidence on either wing from the design and it flew very well. Knife edge with about 8% aileron and rudder coupling was wonderful. Ground handling and landings were easy to manage as it has excellent rudder authority.

I never thought of Dave's design as deficient or flawed, but I did chose to modify (well documented) a few things to make the airframe more capable of handling the extra power of the big Satio.

IMO, if looking at 2-stroke, the Moki/Mark 135 is overdoing it. The lighter OS120AX (sweet engine) would be my choice as well. If I was to build another one, and was going 4-stroke, it would still be the 180 for me. No on-board, and (2) aileron servos (8411's or something equivalent). I did blow one 70 oz aileron servo in flight early on. No flutter and got it down safely.

I must tell you one more thing, I think. One day, it just wasn't 'feeling' right in the air as i did my normal routine. I cut it short and landed. This is when I discovered, to my astonishment, that the front dowel pins in the bottom wing were gone and so were the wing bolts!!!! The wing had been hanging like a parasol from the I struts and cabanes. I just can't imagine many bipes surviving that, but my Cermark Pitts did.

Opinions vary, argue incidence or whatever (opinions vary on this as well) but IMO, the Cermark Pitts is one of the best, and with a 180 or 120AX, hold on and have fun.

(in reply to V2PLUS10)

Post #: 32

RE: Cermark Pitts Build/Assembly - 6/25/2007 12:21:58 AM

V2PLUS10

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I agree with the 2 vs 4 aileron servos....two really are enough...the Pitts is pretty responsive and the roll rate is pretty high. I fly mine with 65% to 70% expo on the aileron just to calm it down a bit. Ground handling is great, and you may want to consider a CF tailwheel assy. There is no question that lighter will fly better...Let us know how it turns out.

I may just pull the onboard out of mine and lighten it up a little....

Randy

(in reply to ram3500-RCU)

Post #: 33

RE: Cermark Pitts Build/Assembly - 6/25/2007 5:10:40 AM

vasek

Posts: 1993
Joined: 1/24/2002
From: centre, QC, CANADA
Status: online

Hi ram, can you direct me to the specs for the mods for a bigger engine pls?

thanx, V.

quote:

ORIGINAL: ram3500-RCU

... but I did chose to modify (well documented) a few things to make the airframe more capable of handling the extra power of the big Satio.

_____________________________

I am a proud Canadian >living in Europe;-)

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Post #: 34

RE: Cermark Pitts Build/Assembly - 7/22/2007 6:47:48 AM

friday

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From: slc, UT, USA
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can anyone tell me what the cg is on the cermark pitts s2b--red color
thanks--ray

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Post #: 35

RE: Cermark Pitts Build/Assembly - 7/22/2007 7:54:00 AM

ram3500-RCU

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quote:

ORIGINAL: vasek

Hi ram, can you direct me to the specs for the mods for a bigger engine pls?

thanx, V.

quote:

ORIGINAL: ram3500-RCU

... but I did chose to modify (well documented) a few things to make the airframe more capable of handling the extra power of the big Satio.

I will look this up for you. We talked about this in another thread.

(in reply to vasek)

Post #: 36

RE: Cermark Pitts Build/Assembly - 7/22/2007 8:07:21 AM

ram3500-RCU

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http://www.rcuniverse.com/forum/fb.asp?m=2242897 This is the link to my list of mods with some pictures as well. The first post in this thread has some good info as well. I didn't need the on-board glow with my 180. Saved that weight.

(in reply to V2PLUS10)

Post #: 37

RE: Cermark Pitts Build/Assembly - 7/22/2007 9:04:14 AM

vasek

Posts: 1993
Joined: 1/24/2002
From: centre, QC, CANADA
Status: online

thanks for the link ram!

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Post #: 38

RE: Cermark Pitts Build/Assembly - 10/7/2007 3:32:43 PM

bladerunner1955

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From: Huntington Beach, CA, USA
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quote:

ORIGINAL: V2PLUS10

I agree with the 2 vs 4 aileron servos....two really are enough...the Pitts is pretty responsive and the roll rate is pretty high. I fly mine with 65% to 70% expo on the aileron just to calm it down a bit. Ground handling is great, and you may want to consider a CF tailwheel assy. There is no question that lighter will fly better...Let us know how it turns out.

I may just pull the onboard out of mine and lighten it up a little....

Randy

I think is is one of my best flying planes to date. It is easy to get back and forth to the field and store. I have converted this Pitts, like all of my planes to electric power. I use an AXI 5330/F3 on 10 cells of lipoly and swing a 20/12 prop. When I fly it at fun flys the gas guys can not believe it is electric. This conversion was the easest conversion I have done. All that was needed was an battery box for the lipolys, and you can insert the lipolys from underneeth though the factory cut out no problem.

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Post #: 39

RE: Cermark Pitts Build/Assembly - 10/7/2007 4:28:19 PM

V2PLUS10

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From: Boise, ID,
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